Biodegradable polymers have very unique properties and thus being widely used in various fields of biomedicine, such as surgical sutures, bone fixation devices, scaffold materials for biological tissue engineering, carriers for controlled-release drugs, and the like. Synthetic biodegradable polymers mainly include aliphatic polyesters (polyglycolide PGA, polylactide PLA, lactide-glycolide copolymer PLGA, polycaprolactone PCL), polycarbonate (polytrimethylene cyclic carbonate PTMC), etc., which are the most commonly used biodegradable polymers, and have been approved by the US Food and Drug Administration (FDA).
However, the existing biodegradable polymers, such as PTMC, PCL, PLA and PLGA, have relatively simple structures, lack of modifiable functional groups, and are usually hard to provide a drug carrier stable in circulation or a stable surface modified coating. The degradation products of polycarbonates are mainly carbon dioxide and neutral glycols, with no acidic degradation products generated. Among these, a functional cyclic carbonate monomer can be copolymerized with cyclic ester monomers such as GA, LA and ε-CL, and other cyclic carbonate monomers, to obtain biodegradable polymers with different properties.
In addition, the biodegradable nanocarriers obtained from the biodegradable polymers prepared by the prior art have the problems of instability in in vivo circulation, low uptake of tumor cells, and low intracellular concentration of drug, which result in the low potency of nanomedicines along with toxic and side effects. Micellar nanoparticles can be prepared from the functional biodegradable polymer, which are stable in in vivo circulation. However, the micellar nanoparticles can only be loaded with hydrophobic small molecule anticancer drugs, but is inability for hydrophilic small molecule anticancer drugs with strong penetrating property and for hydrophilic bio-macromolecular drugs having low toxic and side effects such as protein drugs and nucleic acid drugs, thus greatly limiting their application as drug carriers.
Cancer is the main killer threatening human health. The morbidity and mortality of cancer have been increasing year by year. The incidence of lung cancer in the world, especially in China, remains high. Surgery can only be beneficial to patients in early stage of lung cancer but ineffective to patients in middle and late stages. The treatment of lung cancer is featured by difficulties in early diagnosis, poor prognosis, easy metastasis and easiness in developing drug resistance. Nanomedicine is a key point and hope for the treatment of lung cancer. However, in the prior art, there is still a lack of high-potency nanomedicines which are stable in in vivo circulation, specifically target lung cancer, release drug rapidly within cells, and have low toxic and side effects. In particular, there is a lack of nanocarriers capable of transporting hydrophilic small molecule anticancer drugs.